The invention relates to mixtures of long-chain alkyl phosphates and to their use as emulsifier, in particular in cosmetic and pharmaceutical emulsions. These esters are notable for being very effective in lowering surface tension, for having high stability, even upon heating, and low sensitivity to electrolytes and acids.
The use of emulsifiers for the preparation of creams, lotions, ointments etc., which comprise two or more immiscible substances (e.g. water, oil, organic and inorganic constituents), has been known for a long time. The emulsifiers used are surfactants, e.g. soaps of alkali metals and alkanolamines, mono- and diglyceryl esters of fatty acids, but also certain naturally occurring substances (e.g. lecithins, waxes) and inorganic substances (e.g. bentonite).
EP-B-0 553 241 discloses the use of mixtures of alkyloligoglucosides, fatty alcohols and, if desired, polyglucose for the preparation of emulsions. WO-92/07543 describes the use of alkyloligoglucosides with fatty alcohols and partial glycerides as cosmetic emulsifiers.
EP-B-0 201 040 describes the emulsifying power of metal salts of dialkyl phosphates, and EP-B-0 227 012 that of monoalkyl phosphates. GB-A-2 139 112 describes an emulsifier mixture consisting of mono- and diphosphate, some of which are also ethoxylated, in a ratio of from 100:0 to 70:30 and also a nonionic surfactant.
The use of .beta.-branched monoalkyl phosphates as emulsifier is described in EP-A-0 265 702.
German Patent Application 197 07 800.1 likewise describes mixtures of mono-, di- and trialkyl phosphates and their use as emulsifiers.